FR2830660A1 - Liquid crystal display having two transparent sections holding liquid crystal layer with mosaic color filters, glass layer and polarizer having thickness following set relationship - Google Patents

Abstract

The liquid crystal reflective mode flat screen has a liquid crystal layer (3) between two transparent sections, and an external light receiving face. One internal face supports the first transparent electrode (6), the second face has an external face (9) reflecting light and a second internal face supporting a transparent electrode (7). The second transparent support has a colored filter (2) made of mosaic elements, a glass layer (13) , and a polarizer (8). The thickness parameters are set to follow a fixed relationship.

Description

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LIQUID CRYSTAL FLAT SCREEN OPERATING IN FASHION
REFLECTIVE AND METHOD FOR PRODUCING THE SAME
DESCRIPTION TECHNICAL FIELD
The invention relates to a liquid crystal flat screen operating in reflective mode. It also relates to a method of producing such a flat screen.

STATE OF THE PRIOR ART
Future portable systems (eg cell phones, smart cards or personal assistants of the future) are integrating more and more functions. The realization of these systems, such as the personal assistants of the future, use many technological bricks. Among these technological bricks are: liquid crystal displays, operating system, microprocessor, batteries. Among these components, screens are those that occupy the most surface and their integration into the system is an important point.

 The mass development of these objects will be realized only if their cost decreases or if they allow different functionalities.

Today, the majority of active matrix flat screens operate in transmissive mode, which results in significant energy consumption.

To solve this problem, other technologies have been developed. These technologies make it possible to obtain screens that operate in

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 reflective, but they are much more complex than those used for transmissive screens.

 One of the challenges in the field of flat screens is therefore to achieve screens that consume less, at a lower cost than known reflective screens.

 In addition, liquid crystal flat screens are mainly made on glass supports. Glass has many advantages (size, cost, etc.). However, he has one main defect which is his shock resistance. The components or devices made on these supports then require the use of additional protections to be able to integrate them into the portable systems. However, for the integration of these components is maximum, it seems interesting to integrate these components on the final support. In many cases, this support can be advantageously plastic. It would then be particularly advantageous to obtain for example a screen on a plastic support which combines both low manufacturing cost, low weight and good shock resistance compared to glass.

This application is particularly interesting for new generation mobile phones.

However, these liquid crystal displays and active matrix require the use of polarizers which are themselves generally plastic. Advantageously, it would be very interesting to use them both as active function (polarization of light) and as a passive function (flexible and robust mechanical support).

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 In addition, for portable systems, such as smart cards but also personal assistants, it is necessary to also have thin components, for weight and flexibility problems (to adapt to that of microchip).

 In another field, different techniques are known for transferring layers from one medium to another medium. For example, the techniques disclosed by T. HAMAGUCHI et al. in Proc. IEDM, 1985, page 688. These techniques are of great interest because they make it possible to transfer a layer made from a first substrate (for example of the SOI type) to another substrate. However, they require the consumption of the first substrate which is destroyed during the process. In addition, they allow the homogeneous transfer of a thin film only through the presence of a buried layer of silicon oxide which can be used as a barrier layer with respect to a chemical etching.

 More recently, other techniques have been proposed to report TFT transistors (made of polysilicon on a glass substrate) on plastic substrates. One can refer to this subject in the article by S. UTSUNOMIYA et al. in Proc. IDS 2000, page 916 or EP-A-0 924 769. These methods are based on the creation of a separation layer on a substrate (generally amorphous silicon) which, after production of components on this layer, will allow the separation and postponement on another

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 substrate. In this case, the separation (or exfoliation) is obtained using irradiation with light (typically a laser-like beam). Such irradiation is however difficult to control for large areas. In fact, an inhomogeneity of illumination must lead to a homogeneous exfoliation, which can lead to a deterioration of the superficial film. This constitutes a significant technological difficulty.

 Among the transfer methods, it is also possible to use thin film transfer methods of materials containing or not all or part of a microelectronic component. These methods are based on the creation of a fragile layer buried in a material from the introduction of one or more gaseous species. On this subject, reference can be made to documents FR-A-2 681 472 (corresponding to US Pat. No. 5,374,564), FR-A-2,748,851 (corresponding to US Pat. No. 6,020,252) and FR-A-2,748,850. (corresponding to US Pat. No. 6,190,998) and FR-A-2,773,261. These methods are generally used with the objective of detaching the assembly of a film from an initial substrate for transfer to a support. The thin film obtained then contains a portion of the substrate. These films can serve as active layers for the production of electronic or optical components. Indeed, the main advantage of these methods is that they make it possible to obtain thin films of monocrystalline substrates on different supports. These films may contain all or part of a component.

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STATEMENT OF THE INVENTION
A first object of the invention is to transform a liquid crystal flat screen, normally designed to operate in transmissive mode, to enable it to operate in reflective mode so as to consume less energy. For example, it is possible to use "Twisted Nematic", "Super Twisted Nematic", "Vertically Aligned" and "In Plane Switching" active matrix flat screens in reflective mode while these screens are working. preferentially in transmissive mode.

 The invention also makes it possible, in a particular embodiment, to obtain screens on supports which are flexible, robust, inexpensive and which make it easier to integrate the screen into its definitive support.

 The invention therefore relates to a liquid crystal flat screen operating in reflective mode comprising a liquid crystal layer of thickness e confined between first transparent confinement means and second transparent confinement means, the first transparent confinement means possessing an outer face, intended to receive light incident on the screen, and an inner surface supporting first transparent electrodes for applying an electric field to the liquid crystal, the second transparent confinement means having an outer face, supporting a reflector for reflecting light passing through the second transparent confinement means, and an inner face supporting second electrodes

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- soit, les premiers moyens de confinement transparents comprennent, entre leur face interne et leur face externe, une couche formant filtre coloré constituée d'une mosaïque d'éléments de largeur l, et les seconds moyens de confinement transparents comprennent, entre leur face interne et leur face externe, une couche de verre ou de Si02 d'épaisseur e3 et d'indice de réfraction n et une couche formant polariseur d'épaisseur e4, les paramètres ei, e3, e4 et l étant choisis de sorte que :

transparent application of an electric field to the liquid crystal, characterized by one of the following alternatives: - either, the second transparent confinement means comprise, between their inner face and their outer face, a thick colored filter layer e2 and consisting of a mosaic of elements of width l, a layer of glass or SiO2 of thickness e3 and of refractive index n and a layer forming polarizer of thickness e4, the parameters ei, e2, e3, e4 and l being chosen so that:

or, the first transparent confinement means comprise, between their inner face and their external face, a colored filter layer consisting of a mosaic of elements of width l, and the second transparent confinement means comprise, between their internal face; and their outer face, a layer of glass or SiO 2 with a thickness e 3 and a refractive index n and a polarizer layer with a thickness e 4, the parameters e 1, e 3, e 4 and 1 being chosen so that:

The reflector may be a metal film.
Advantageously, the polarizer layer of the second transparent confinement means is made of plastic.

 Preferably, the first transparent confinement means comprise, respectively,

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 between their inner face and their outer face, a glass slide and a polarizer layer. This polarizer layer may be plastic.

 Advantageously, the first transparent confinement means or the second transparent confinement means support an active matrix associated with the transparent electrodes supported by these transparent confinement means.

 The invention also relates to a method for producing a liquid crystal flat screen comprising a liquid crystal layer confined between first transparent confinement means and second transparent confinement means, the method comprising the following steps: a structure comprising vis-à-vis said first transparent confinement means and a support, said first transparent confinement means having a face external to the structure for receiving light incident on the screen and an inner face to the structure supporting first transparent electrodes for applying an electric field to the liquid crystal, the portion of the support facing the first transparent confinement means being made of glass or of Si02 of refractive index n and supporting a colored filter layer of thickness e2 and constituted by a mosaic of elements of width l, the layer f ormant colored filter supporting second transparent electrodes for applying an electric field to the liquid crystal, a liquid crystal layer of thickness ei being confined between the

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la couche formant filtre coloré, la couche de verre ou de Si02 et la couche formant polariseur constituant lesdits seconds moyens de confinement transparents, - mise en place d'un réflecteur destiné à réfléchir de la lumière traversant les seconds moyens de confinement transparents sur la face libre de la couche formant polariseur. first transparent confinement means and the color filter layer; thinning the support in order to keep only one layer of glass or SiO 2 with a thickness e 3 and a refractive index n adjacent to the colored filter layer; a polarizer layer of thickness e4 on the free face of the glass or SiO 2 layer, the parameters e 1, e 2, e 3, e 4 and 1 being chosen so that:

the color filter layer, the glass or SiO 2 layer and the polarizer layer constituting said second transparent confinement means, - placing a reflector for reflecting light passing through the second transparent confinement means on the face free of the polarizer layer.

 According to a first variant of implementation, during the step of producing the structure, said first transparent confinement means used are confinement means comprising respectively, between their internal face and their external face, a glass slide and a polarizer forming layer. According to a second variant of implementation, during the step of producing the structure, said first transparent confinement means used comprise only a glass slide, the method comprising an additional step, subsequent to the step of thinning of the support, consisting in arranging a polarizer on the blade of

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 glass of the first transparent confinement means, on the external face side of the structure.

 Thinning of the support can be achieved by a method selected from grinding, chemical mechanical polishing and chemical etching.

 According to an alternative embodiment, during the step of producing the structure, the support used comprises said layer of glass or SiO 2 of thickness e 3 and of refractive index n separated from the rest of the support by a barrier layer , the step of thinning the support consisting of eliminating the rest of the support first and then removing the barrier layer. Removal of the rest of the support can be achieved by etching. The removal of the barrier layer can be carried out by chemical etching.

 According to another variant embodiment, during the step of producing the structure, the support used comprises said layer of glass or SiO 2 with a thickness e 3 and a refractive index n separated from the rest of the support by a separation layer , the step of thinning the support consisting of removing the rest of the support to the separation layer.

 If, during the step of producing the structure, said first confinement means are part of a thick substrate, the method may then further comprise a step of thinning the thick substrate to retain only the first means of containment.

 Advantageously, during the step of producing the structure, an active matrix is

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 associated with the first transparent electrodes or the second transparent electrodes.

 The invention also relates to a method for producing a liquid crystal flat screen comprising a liquid crystal layer confined between first transparent confinement means and second transparent confinement means, the method comprising the following steps: a structure comprising vis-à-vis said first transparent confinement means and a support, said first transparent confinement means having a face external to the structure for receiving light incident on the screen and an inner face to the structure supporting a color filter layer consisting of a mosaic of elements of width l, the color filter layer supporting first transparent electrodes for applying an electric field to the liquid crystal, the part of the support lying in contact with with respect to the first transparent confinement means being made of glass or SiO 2 having a refractive index n and supporting second transparent electrodes for applying an electric field to the liquid crystal, a liquid crystal layer of thickness ei being confined between the second transparent confinement means and the color filter layer, - thinning of the support to conserve a layer of glass or SiO 2 with a thickness e 3 and a refractive index n supporting the second transparent electrodes,

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la couche de verre ou de Si02 et la couche formant polariseur constituant lesdits seconds moyens de confinement transparents, - mise en place d'un réflecteur destiné à réfléchir de la lumière traversant les seconds moyens de confinement transparents sur la face libre de la couche formant polariseur. gluing a layer forming a polarizer of thickness e4 on the free face of the layer of glass or SiO 2, the parameters e 1, e 1, e 4 and 1 being chosen so that:

the layer of glass or SiO 2 and the polarizer layer constituting said second transparent confinement means, - placing a reflector for reflecting light passing through the second transparent confinement means on the free face of the polarizer layer .

 According to a first implementation variant, during the step of producing the structure, said first transparent confinement means used are confinement means comprising respectively, between their internal face and their external face, the colored filter layer, a glass slide and a polarizer layer. According to a second variant of implementation, during the step of producing the structure, said first transparent confinement means used comprise only a glass slide and the colored filter layer, the method comprising an additional, later step at the step of thinning the support, consisting in arranging a polarizer on the glass slide of the first transparent confinement means, on the external face side of the structure.

 Thinning of the support can be achieved by a method selected from grinding, chemical mechanical polishing and chemical etching.

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 According to an alternative embodiment, during the step of producing the structure, the support used comprises said layer of glass or SiO 2 of thickness e 3 and of refractive index n separated from the rest of the support by a barrier layer , the step of thinning the support consisting of eliminating the rest of the support first and then removing the barrier layer. Removal of the rest of the support can be achieved by etching. The removal of the barrier layer can be carried out by chemical etching.

 According to another variant embodiment, during the step of producing the structure, the support used comprises said layer of glass or SiO 2 with a thickness e 3 and a refractive index n separated from the rest of the support by a separation layer , the step of thinning the support consisting of removing the rest of the support to the separation layer.

 If, during the step of producing the structure, said first confinement means are part of a thick substrate, the method may then further comprise a step of thinning the thick substrate to retain only the first means of containment.

 Advantageously, during the step of producing the structure, an active matrix is associated with the first transparent electrodes or the second transparent electrodes.

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BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and other advantages and particularities will appear on reading the following description, given by way of non-limiting example, accompanied by the appended drawings in which: FIG. 1 is a cross-sectional view of a stacked structure intended for the production of a liquid crystal flat screen according to the invention; FIG. 2 represents the structure of FIG. 1 in a more advanced embodiment; FIG. 3 is a sectional view transverse of a liquid crystal flat screen according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The invention consists in taking at least one of the parts constituting the flat screen, which are very thin (screen and addressing circuit) and which are produced on a rigid glass support, and then transfer them directly to a reflective polarizer, that is to say a polarizer associated with a thin reflective layer generally consisting of a metal film. A very small distance is thus obtained between, on the one hand, the image plane consisting of the liquid crystal layer, itself located a few tenths of a micrometer from the colored filters, and on the other hand the reflective plane. This proximity makes the

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 optical system obtained without any parallax effect visible to the eye, provided that certain geometrical constraints are respected.

 Figure 1 is a cross-sectional view of a stacked structure for the realization of a liquid crystal flat screen according to the invention.

 The structure is constituted on a support 10 comprising a glass plate 11 supporting a first layer 12 and a second layer 13. The glass plate 11 is for example a large plate, such as those used for the manufacture of crystal screens liquid. It may be a 1737 glass plate from Corning. On the plate 11 is deposited a layer 12 which will serve as a barrier layer. The layer 12 may be amorphous silicon or polycrystalline and have 300 nm thick.

These materials can be deposited by LPCVD. In some cases, before the deposition of the layer 12, an intermediate layer may be deposited on the plate 11 to promote adhesion. This intermediate layer is for example a silicon oxide layer.

 The layer 13 is deposited on the layer 12.

This is for example a layer of silicon oxide with a thickness of 0.5! lm to 5! lm for example. The layer 13 is of a nature close to that of the plate 11.

 On the support 10, a liquid crystal screen is produced in a manner identical to that used on a standard substrate. It may be advantageous to carry out on this type of support at least every

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 control circuits. Typically, this technology does not involve temperatures above 4000C.

 The structure obtained comprises, superimposed on the support 10, a colored filter 2 of thickness e2, consisting of a mosaic of elements of width l, a liquid crystal layer 3, a glass plate 4 and a layer 5 forming polarizer and fixed by gluing. The glass slide 4 supports, on the liquid crystal side, a set of electrodes 6. The colored filter 2 supports, on the liquid crystal side, a set of electrodes 7.

 Once the structure is completed, the support 10 is thinned. To obtain this thinning, it is possible to use a technique, alone or in combination, chosen from grinding, mechanical polishing, chemical mechanical polishing, wet or dry chemical attack. For example, the plate 11 can be ground to a thickness of about 80 μm and thinning can be continued by means of a solution of HF. To attack only the face to be thinned, it is possible for example to use a "spin etcher" or to protect the front face and the sides of the structure.

 Once the plate 11 has been removed, the etching stops on the silicon layer 12 which is not etched by the HF solution. The layer can then be removed using a chemical etching (TMAH, KOH or other). TMAH is interesting because it has a good attack selectivity with SiO 2. The structure shown in FIG. 2 is obtained.

 In an alternative embodiment, the polarizer layer 5 can be glued after thinning of the support 10.

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 FIG. 3 shows the flat screen obtained after the bonding of a layer 8 forming a polarizer on the free face of the layer 13 and the attachment of a reflector 9 on the free face of the layer 8, the device can then operate in reflective mode.

avec : el épaisseur du cristal liquide 3, e2 épaisseur du filtre coloré 2, e3 épaisseur de la couche 13, e4 épaisseur de la couche 8, n indice de réfraction de la couche 13,
1 largeur d'un élément du filtre coloré 2. The condition for not having a visible parallax effect is expressed by the following relation:

with: the thickness of the liquid crystal 3, e2 the thickness of the colored filter 2, e3 the thickness of the layer 13, e4 the thickness of the layer 8, n the refractive index of the layer 13,
1 width of a colored filter element 2.

peut être de 50 m. Le filtre coloré 2 peut supporter des électrodes transparentes 7 en ITO d'environ 0, 1 m d'épaisseur. La couche de cristal liquide 3 peut avoir une épaisseur ei de 5 Mm. The thickness e4 of the polarizer layer 8 may be 5 m. The thickness e2 of the color filter 2 may be 1 m and the width 1 of an element

can be 50 m. The color filter 2 can support transparent electrodes 7 of ITO about 0.1 m thick. The liquid crystal layer 3 may have a thickness ei of 5 Mm.

 Under these conditions, if the refractive index n of the layer 13 is 1.4, the thickness e3 of the layer 13 must be less than 9 m.

Claims (26)

A liquid crystal flat screen operating in reflective mode comprising a layer of liquid crystal (3) of thickness ei confined between first transparent confinement means and second transparent confinement means, the first transparent confinement means having an external face. , intended to receive light incident on the screen, and an inner surface supporting first transparent electrodes (6) for applying an electric field to the liquid crystal, the second transparent confinement means having an external surface, supporting a reflector (9) for reflecting light passing through the second transparent confinement means, and an inner face supporting second transparent electrodes (7) for applying an electric field to the liquid crystal, characterized by one of the following alternatives or the second transparent confinement means comprise, between their internal face and their an outer layer, a color filter layer (2) of thickness e2 and consisting of a mosaic of elements of width l, a layer of glass or SiO 2 (13) with a thickness e 3 and a refractive index n and a polarizer layer (8) of thickness e4, the parameters Ci, e2, e3, e4 and l being chosen so that:

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 or, the first transparent confinement means comprise, between their inner face and their external face, a colored filter layer consisting of a mosaic of elements of width l, and the second transparent confinement means comprise, between their internal face; and their outer face, a layer of glass or SiO 2 with a thickness e 3 and a refractive index n and a polarizer layer with a thickness e 4, the parameters e 1, e 3, e 4 and 1 being chosen so that: 2. flat screen liquid crystal according to claim 1, characterized in that the reflector (9) is a metal film.  3. Flat screen liquid crystal according to one of claims 1 or 2, characterized in that the polarizer layer (8) of the second transparent confinement means is plastic.  4. Flat screen liquid crystal according to any one of claims 1 to 3, characterized in that the first transparent confinement means respectively comprise, between their inner face and their outer face, a glass slide (4) and a layer forming polarizer (5). <Desc / Clms Page number 19>  5. flat screen liquid crystal according to claim 4, characterized in that the polarizer layer (5) of the first transparent confinement means is plastic.  6. Flat screen liquid crystal according to any one of claims 1 to 5, characterized in that the first transparent confinement means or the second transparent confinement means support an active matrix associated with the transparent electrodes supported by these means of transparent confinement .  7. A method of producing a liquid crystal flat screen comprising a liquid crystal layer (3) confined between first transparent confinement means and second transparent confinement means, the method comprising the following steps: - realization of a structure comprising vis-à-vis said first transparent confinement means and a support (10), said first transparent confinement means having a face external to the structure intended to receive light incident on the screen and an inner face to the structure supporting first transparent electrodes (6) for applying an electric field to the liquid crystal, the portion of the support facing the first transparent confinement means being made of glass or refractive index Si02 n and supporting a color filter layer (2) <Desc / Clms Page number 20>  SiO 2 (13), the parameters e1, e2, e3, e4 and l being chosen such that: in x1 - + e2 + e3 + e4 <2 4 the color filter layer (2), the glass or SiO 2 (13) and the polarizer layer (8) constituting said second transparent confinement means, - setting up a reflector (9) for reflecting light passing through the second transparent confinement means on the face free of the polarizer layer (8).

 of thickness e2 and consisting of a mosaic of elements of width l, the color filter layer (2) supporting second transparent electrodes (7) for applying an electric field to the liquid crystal, a layer of liquid crystal (3) of thickness ei being confined between the first transparent confinement means and the color filter layer (2), - thinning of the support (10) to retain only one layer of glass or SiO 2 (13) of thickness e3 and refractive index n adjacent to the color filter layer (2), - gluing a polarizer layer (8) of thickness e4 on the free face of the  8. Method according to claim 7, characterized in that, during the step of producing the structure, said first transparent confinement means used are containment means respectively comprising, between their internal face and <Desc / Clms Page number 21>  their outer face, a glass slide (4) and a polarizer layer (5).  9. Method according to claim 7, characterized in that, during the step of producing the structure, said first transparent confinement means used comprise only a glass slide (4), the method comprising an additional step, after the step of thinning the support (10), consisting in arranging a polarizer (5) on the glass slide (4) of the first transparent confinement means, on the outer face of the structure.  10. The method of claim 7, characterized in that the thinning of the support (10) is achieved by a method selected from rectification, chemical mechanical polishing and chemical etching.  11. A method according to claim 7, characterized in that, during the step of producing the structure, the support (10) used comprises said layer of glass or SiO 2 (13) of thickness e 3 and index of refraction n separated from the rest (11) of the support by a stop layer (12), the step of thinning the support consisting of first removing the rest (11) of the support and then removing the stop layer ( 12). <Desc / Clms Page number 22>  12. The method of claim 11, characterized in that the removal of the rest (11) of the support is obtained by etching.  13. The method of claim 11, characterized in that the removal of the barrier layer (12) is performed by chemical etching.  14. The method as claimed in claim 7, characterized in that, during the step of producing the structure, the support used comprises said layer of glass or SiO 2 with a thickness e 3 and a refractive index n separated from the remainder of the supported by a separating layer, the step of thinning the support comprising removing the remainder of the support to the separation layer.  15. The method as claimed in claim 7, characterized in that, during the step of producing the structure, said first confinement means are part of a thick substrate, the method then furthermore comprising a thinning stage of this thick substrate to keep only the first means of containment.  16. Method according to any one of claims 7 to 15, characterized in that, during the step of producing the structure, an active matrix is associated with the first transparent electrodes or the second transparent electrodes. <Desc / Clms Page number 23>  17. A method of producing a flat screen liquid crystal comprising a liquid crystal layer confined between first transparent confinement means and second transparent confinement means, the method comprising the following steps: - realization of a structure comprising with respect to said first transparent confinement means and a support, said first transparent confinement means having a face external to the structure for receiving light incident on the screen and an inner face to the structure supporting a layer forming colored filter consisting of a mosaic of elements of width l, the color filter layer supporting first transparent electrodes for applying an electric field to the liquid crystal, the part of the support situated opposite the first means transparent confinement being made of glass or SiO2 of refractive index n and supporting transparent electrodes for applying an electric field to the liquid crystal, a liquid crystal layer of thickness ei being confined between the second transparent confinement means and the colored filter layer, thinning of the support to keep only one layer of glass or SiO 2 with a thickness e 3 and a refractive index n supporting the second transparent electrodes, - bonding a layer forming a polarizer of thickness e 4 on the free face of the glass layer <Desc / Clms Page number 24>  the layer of glass or SiO 2 and the polarizer layer constituting said second transparent confinement means, - placing a reflector for reflecting light passing through the second transparent confinement means on the free face of the polarizer layer .

 or Silos, the parameters el,! e3! e4 and l being chosen so that:  18. A method according to claim 17, characterized in that, during the step of producing the structure, said first transparent confinement means used are confinement means comprising respectively, between their internal face and their outer face, the layer. color filter, a glass slide and a polarizer layer.  19. Method according to claim 17, characterized in that, during the step of producing the structure, said first transparent confinement means used comprise only a glass slide and the colored filter layer, the method comprising a additional step, subsequent to the step of thinning the support, consisting in arranging a polarizer on the glass slide of the first transparent confinement means, on the outer face side of the structure. <Desc / Clms Page number 25>  20. The method of claim 17, characterized in that the thinning of the support is achieved by a method selected from grinding, chemical mechanical polishing and chemical etching.  21. A method according to claim 17, characterized in that, during the step of producing the structure, the support used comprises said glass or SiO 2 layer of thickness e 3 and of refractive index n separated from the rest of the structure. support by a stop layer, the step of thinning the support consisting of first removing the rest of the support and then removing the barrier layer.  22. The method of claim 21, characterized in that the elimination of the rest of the support is obtained by etching.  23. The method of claim 21, characterized in that the removal of the barrier layer is performed by chemical etching.  24. Process according to claim 17, characterized in that, during the step of producing the structure, the support used comprises said layer of glass or SiO 2 with a thickness e 3 and a refractive index n separated from the rest of the structure. supported by a separating layer, the step of thinning the support comprising removing the remainder of the support to the separation layer. <Desc / Clms Page number 26>  25. The method as claimed in claim 17, characterized in that, during the step of producing the structure, said first confinement means form part of a thick substrate, the method then furthermore comprising a step of thinning of said structure. thick substrate to keep only the first means of containment.  26. Method according to any one of claims 17 to 25, characterized in that, during the step of producing the structure, an active matrix is associated with the first transparent electrodes or the second transparent electrodes.